The move comes on the same day that House Oversight Chair Darrell Issa has scheduled a contempt vote against Obama's Attorney General Eric Holder over his refusal to turn over documents related to the Operation Fast and Furious, in which U.S. agents allowed guns to "walk" across the border into Mexico.

Although most people are just tuning in to the Fast and Furious fracas, the controversy has actually been quietly brewing in Congress for more than a year. But Obama's use of executive privilege — the first such action of his presidency — has upped the political profile of the gun-running scandal, which has become a touchstone election year issue for conservatives.

Here's a breakdown of what went down with Operation Fast and why the scandal is exploding today:

What Was Operation Fast and Furious?

Operation Fast and Furious was launched in 2009 by top DOJ officials, in collaboration with the FBI, the Drug Enforcement Agency, and the Bureau of Alcohol, Tobacco, and Firearms (ATF) as part of a strategy to identify and eliminate arms trafficking networks. Instead of prosecuting the individual “straw purchasers” who buy guns for the cartels, ATF agents would track the guns to the top bosses of Mexico's powerful drug cartels.

As Democrats frequently point out, the "gun-walking" strategy was actually started by the Bush administration in 2006. But Fast and Furious was the biggest gun-walking operation that the DOJ had ever undertaken.

Between 2009 and 2011, ATF agents allowed more than 2,000 firearms to "walk" across the border. As many as 1,700 of those weapons have since been lost, and more than 100 have been found at bloody crime scenes on both sides of the border, including the murder of a U.S. Border Patrol agent in Arizona last December.

How Did It Turn Into Such A Big Scandal?

ATF whistle-blowers blew the lid off of Operation Fast and Furious shortly after the Border Patrol Agent's death, prompting House Republicans to open up an investigation into who knew what about the gun-smuggling operation.

In a Feb. 4, 2011 letter to Issa and Sen. Charles Grassley, the ranking Republican on the Senate Judiciary Committee, the Justice Department denied the existence of Operation Fast and Furious, writing that the “ATF makes every effort to interdict weapons that have been purchased illegally and prevent their transportation to Mexico.”

Holder also came under fire from Congress, after he told the Oversight Committee in May 2011 that he first heard of Fast and Furious "over the last few weeks." But Congress later obtained internal DOJ memos related to the Operation that were addressed to Holder and dated from Sept. 2010.

In a letter to Holder this week, Issa explained that the House Oversight Committee needs those documents to "understand what the Department knew about Fast and Furious, including when and how it discovered its February 4 letter was false, and the Department's efforts to conceal that information from Congress and the public."

In short, Issa wants to determine if and how the Obama administration covered up its involvement in the Fast and Furious scandal.

Obama's executive privilege now protects those post-Feb. 4 documents from Congressional subpoena, meaning that the DOJ won't have to give Issa the documents.

In his request for executive privilege, Holder argued that the documents should be protected from subpoena because they were not related to Operation Fast and Furious, but rather to how DOJ was going to respond to congressional and media inquiries about the operation.

You can read Holder's entire letter here. But basically, Holder is arguing that the House Oversight Committee can't have oversight over how the Executive branch responds to an investigation.

Here's the key excerpt:

"Congressional oversight of the process by which the Executive Branch responds to congressional oversight inquiries would create a detrimental dynamic that is quite similar to what would occur in litigation if lawyers had to disclose to adversaries their deliberations about the case, and specifically about how to respond to their adversaries' discovery requests….

A congressional power to request information from the Executive Branch and then review the ensuing Executive Branch discussions regarding how to respond to that request would chill the candor of those Executive Branch discussions and introduce significantly unfair imbalance to the oversight process."

Can Congress Overturn Obama's Executive Privilege?

Technically, Congress can overturn executive privilege, if it can prove that the documents are "demonstrably critical" to its investigation. But as Holder points out, the documents Issa wants relate to the DOJ's response to the investigation — not to the investigation itself.

Who Is Right?

Actually, both sides have a pretty strong argument.

As far as we can tell, the legal premise of Holder's argument is sound — allowing the House to control how the executive branch responds to investigations would be a violation of the balance of powers. Plus, there's precedent — previous presidents, including George W. Bush and Bill Clinton, used executive privilege for the same reasons that Holder lays out.

On the GOP side, Obama's decision to further enshroud the Fast and Furious scandal in secrecy confirms Republican suspicions that the administration is hiding something, and is possibly trying to cover up who knew what about the botched gun-walking program.

In the end, however, the entire debacle will probably be a wash, at least as far as election-year politics are concerned. People who hate Obama already will hate him even more after today, but everybody else will likely dismiss the news as more theatrics from a Congress that doesn't do much except yell at people.